An image-side telecentric optical system has important applications. For example, the image-side telecentric optical system can be used to eliminate a change in system magnification caused by an axial displacement of an image plane. The image-side telecentric optical system can enhance a relative illumination of an image plane in an entire field of view. The image-side telecentric optical system can be used to eliminate unevenness of CCD color in RGB three-color.
If the image-side telecentric system is combined with an off-axis three-mirror optical system, the color difference can be reduced and the central obscuration can be eliminated. However, the optical system will produce a series of asymmetric aberrations after off-axis, and it is difficult to use conventional rotationally symmetric surfaces to correct the asymmetric aberrations. In addition, the image-side telecentric will increase the design difficulty of the off-axis three-mirror optical system.